Healthy Lemieux almost assuredly breaks Gretzky's single season goal and points record in 92-93, obviously not the assist mark no one is ever breaking that. One might question whether he could achieve it in 80 games but remember, that season had
84 games. At Lemieux's scoring rate that amounts to an extra 11 points. Also Lemieux actually put up his 160 points in about
58 games, not 60. He missed about 2 extra games worth of ice time that season, for reasons that's been well documented
here. That means he would have 26 games to put up 24 goals and 56 points - a relatively modest 2.15ppg. It's highly unlikely that a healthy Lemieux would perform below that level.
Career total's are another matter. If we're being fair to Gretzky we should also assume no back injury for him in 91-92 either which most likely puts him over 3,000. He did have the benefit of playing those 5 extra years 80-85 in the highest scoring era, while Lemieux would have to make that up with 5 years in the DPE and that's just not happening - and some people don't think I'm reasonable. Still I do think Mario has the career goals mark either way.
Also, we also shouldn't assumed that Lemieux, or Orr, wouldn't miss any time at all. It's unrealistic to expect a full career from either with zero missed games. Minor injuries would still occur here and there and cost them some time, though of course far less. If so, then for this scenario we probably shouldn't assume any major changes prior the 1989-90 season for Lemieux, as it appears he only missed one game(in 85-86) due to a back-related injury;
Hockeycentral | Mario Lemieux | Medical Record